Rotor blade for wind turbine

ABSTRACT

A rotor blade for a wind turbine and a method for reducing rotor blade noise are disclosed. The rotor blade includes a body having exterior surfaces defining a pressure side, a suction side, a leading edge, and a trailing edge extending between a tip and a root, the surfaces further defining an interior. The rotor blade further includes at least one purge conduit defined in the tip and configured for exhausting air from the interior such that the air generally reduces noise at the tip.

FIELD OF THE INVENTION

The present disclosure relates in general to wind turbine rotor blades, and more particularly to noise reduction features defined in the rotor blades.

BACKGROUND OF THE INVENTION

Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, generator, gearbox, nacelle, and one or more rotor blades. The rotor blades capture kinetic energy of wind using known foil principles. The rotor blades transmit the kinetic energy in the form of rotational energy so as to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid.

During operation of the wind turbine, the rotor blades may produce noise of varying frequencies due to the flow of air past the rotor blades. As wind turbines are increasingly located near populated areas, this noise can be disruptive to the populace and thus is generally undesirable.

One specific form of noise that may be produced by the rotor blades is a generally high frequency broadband noise caused by flow vortices at the tip of the rotor blade. The flow vortices are generally caused by the interaction of flow over the tip from the pressure side and the suction side. The flow vortices may then interact with the tip and the trailing edge of the rotor blade, causing the generally high frequency broadband noise. Additionally, the flow vortices may disturb streamline flows off of the pressure side and the suction side near the tip, thus reducing the performance of the rotor blade.

Thus, improved apparatus and methods for reducing the noise associated with a rotor blade, and specifically with the tip of a rotor blade, would be desired. For example, apparatus and methods for reducing the noise caused by tip flow vortices would be advantageous.

BRIEF DESCRIPTION OF THE INVENTION

Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.

In one embodiment, a rotor blade for a wind turbine is disclosed. The rotor blade includes a body having exterior surfaces defining a pressure side, a suction side, a leading edge, and a trailing edge extending between a tip and a root, the surfaces further defining an interior. The rotor blade further includes at least one purge conduit defined in the tip and configured for exhausting air from the interior such that the air generally reduces noise at the tip.

In another embodiment, a method for reducing rotor blade noise is disclosed. The method includes flowing air through an interior of the rotor blade. The rotor blade includes a body having exterior surfaces defining a pressure side, a suction side, a leading edge, and a trailing edge extending between a tip and a root, the surfaces further defining the interior. The method further includes flowing at least a portion of the air through at least one purge conduit defined proximate the tip of the rotor blade, and exhausting at least a portion of the air from the purge conduit such that the air interferes with a tip flow vortex and generally reduces noise at the tip.

These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which:

FIG. 1 is a perspective view of a wind turbine according to one embodiment of the present disclosure;

FIG. 2 is a perspective view of a rotor blade according to one embodiment of the present disclosure;

FIG. 3 is a front view of a tip defining a plurality of purge conduits according to one embodiment of the present disclosure;

FIG. 4 is a front view of a tip defining a plurality of purge conduits according to another embodiment of the present disclosure;

FIG. 5 is a cross-sectional view, through the lines 5-5 of FIG. 3, of a tip defining a plurality of purge conduits according to one embodiment of the present disclosure;

FIG. 6 is a cross-sectional view of a tip defining a plurality of purge conduits according to another embodiment of the present disclosure; and,

FIG. 7 is a perspective view of a portion of a rotor blade including a tip defining a plurality of purge conduits and further including a stagnation zone according to one embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.

FIG. 1 illustrates a wind turbine 10 of conventional construction. The wind turbine 10 includes a tower 12 with a nacelle 14 mounted thereon. A plurality of rotor blades 16 are mounted to a rotor hub 18, which is in turn connected to a main flange that turns a main rotor shaft. The wind turbine power generation and control components are housed within the nacelle 14. The view of FIG. 1 is provided for illustrative purposes only to place the present invention in an exemplary field of use. It should be appreciated that the invention is not limited to any particular type of wind turbine configuration.

Referring to FIG. 2, a rotor blade 16 according to the present disclosure comprises a body 20. The body 20 may include exterior surfaces defining a pressure side 22 and a suction side 24 (see FIGS. 3 through 7) extending between a leading edge 26 and a trailing edge 28 and between a blade tip 32 and a blade root 34. The tip 32 may, for purposes of the present disclosure, be the generally outermost surface of the body 20. As shown in FIGS. 5 and 6, for example, the tip 32 may comprise and extend between exterior surface 36 and interior surface 38. Further, the various surfaces of the body 20 may define an interior 40 (see FIGS. 5 through 7) of the rotor blade 16.

The rotor blade 16 may further define chord 42 and a span 44. As shown in FIG. 2, the chord 42 may vary throughout the span 44 of the rotor blade 16. Thus, as discussed below, a local chord 46 may be defined for the rotor blade 16 at any point on the rotor blade 16 along the span 44. For example, as shown in FIGS. 2 through 4 and 7, a local chord 46 may be defined at the tip 32, as well as at any other location throughout the span 44 of the rotor blade 16.

In some embodiments, the rotor blade 16 may include a plurality of individual blade segments aligned in an end-to-end order from the blade tip 32 to the blade root 34. Each of the individual blade segments may be uniquely configured so that the plurality of blade segments define a complete rotor blade 16 having a designed aerodynamic profile, length, and other desired characteristics. For example, each of the blade segments may have an aerodynamic profile that corresponds to the aerodynamic profile of adjacent blade segments. Thus, the aerodynamic profiles of the blade segments may form a continuous aerodynamic profile of the rotor blade 16. Alternatively, the rotor blade 16 may be formed as a singular, unitary blade having the designed aerodynamic profile, length, and other desired characteristics.

The rotor blade 16 may, in exemplary embodiments, be curved. Curving of the rotor blade 16 may entail bending the rotor blade 16 in a generally flapwise direction and/or in a generally edgewise direction. The flapwise direction may generally be construed as the direction (or the opposite direction) in which the aerodynamic lift acts on the rotor blade 16. The edgewise direction is generally perpendicular to the flapwise direction. Flapwise curvature of the rotor blade 16 is also known as pre-bend, while edgewise curvature is also known as sweep. Thus, a curved rotor blade 16 may be pre-bent and/or swept. Curving may enable the rotor blade 16 to better withstand flapwise and edgewise loads during operation of the wind turbine 10, and may further provide clearance for the rotor blade 16 from the tower 12 during operation of the wind turbine 10.

During operation of the wind turbine 10, the air flowing past the rotor blade 16 may create various forms of noise. For example, air flowing past the rotor blade 16 may form at least one tip flow vortex 50 (see FIGS. 5 through 7), or a plurality of tip flow vortices 50, at or adjacent to the tip 32. These tip flow vortices 50 may be caused by, for example, the interaction of air flows over the tip 32 from the pressure side 22 and the suction side 24, or any other such air flows. The air flow vortices 50 may interact with, for example, the tip 32 and/or the trailing edge 28 of the rotor blade 16 and/or other portions of the rotor blade 16, causing noise. In many cases, the noise may be generally high frequency broadband noise. Additionally, the air flow vortices 50 may disturb streamline flows off of the pressure side 22 and the suction side 24 near the tip 32, thus reducing the performance of the rotor blade 16. Thus, it is generally desirable to reduce or eliminate noise associated with the tip 32 of the rotor blade 16, and specifically to reduce or eliminate noise associated with the tip flow vortices 50.

As illustrated in FIGS. 2 through 7, the rotor blade 16 of the present disclosure may thus include at least one purge conduit 100 or a plurality of purge conduits 100. The purge conduits 100 may be defined in the tip 32. As discussed below, the purge conduits 100 may be configured for exhausting air 102 (see FIGS. 5 through 7) from the interior 40 such that the air 102 generally reduces noise at the tip 32. For example, the air 102 may generally reduce noise at the tip 32 by interacting with flow vortices at the tip to reduce the strength of the vortices and the interaction of the vortices with the rotor blade 16 surfaces at and/or adjacent to the tip 32, thus reducing noise at the tip 32.

It should be understood that the term “air” as used herein encompasses any suitable fluid, such as any suitable gas, that may be flowed through the interior 40 of the rotor blade 16 as discussed herein.

As shown in FIGS. 5 through 7, air 102 may flow through the interior 40 of the rotor blade 16. The air 102 may be supplied to the interior 40 in any suitable manner and through any suitable location or component of the rotor blade 16. For example, the air 102, or a portion thereof, may in some embodiments be supplied to the interior 40 through the root 34. In some embodiments, the air 102, or at least a portion thereof, may be supplied through a stagnation zone 104 on the rotor blade 16, as shown in FIG. 7.

The stagnation zone 104, in general, may be a zone on the exterior of the body 20 where air flow past the rotor blade 16 initially contacts the body 20. The location of the stagnation zone 104 is typically based on the angle of attack of the rotor blade 16 and the direction of the air flow past the rotor blade 16. In exemplary embodiments, the stagnation zone 104, or at least a portion thereof, is located on or adjacent to the leading edge 26. However, portions of the stagnation zone 104 or the entire stagnation zone 104 may alternatively be located on or adjacent to any suitable exterior surface of the body 20, such as on the pressure side 22 or the suction side 24.

To supply air 102 to the interior 40 of the body 20 through the stagnation zone 104, an intake conduit 106 or a plurality of intake conduits 106 may be defined in the stagnation zone 104. The intake conduits 106 may be configured to flow air 102 to the interior 40 of the body 20. For example, the intake conduits 106 may generally be tubes or other suitable conduits extending through the body 20 into the interior 40. The intake conduits 106 may have any suitable cross-sectional shape and/or area, and may taper and/or bend as desired to optimize the amount of air 102 flowed into the interior 40. The air 102 may be a portion of the air flow past the rotor blade 16. When the air flow initially contacts the rotor blade 16, a portion of the air flow, designated as air 102, may be flowed into and through the intake conduits 106, and into the interior 40.

In some exemplary embodiments, the intake conduits 106 may be located relatively near the tip 32. Thus, for example, the intake conduits 106 may in some embodiments be located between approximately 0% and approximately 5% of the span 42 from the tip 32. It should be understood, however, that the present disclosure is not limited to this range of locations, and rather that any suitable intake conduit 106 location is within the scope and spirit of the present disclosure.

As discussed above, the air 102, or a portion thereof, may be supplied to the interior 40 in any other suitable manner and through any suitable location or component of the rotor blade 16. The air 102 in the interior 40 of the rotor blade 16 may, during operation of the wind turbine 10, flow through the interior 40 of the rotor blade 16. For example, centrifugal forces due to rotation of the rotor blades 16 may cause the air 102 in the interior 40 to flow generally towards the tip 32. The flow of air 102 towards the tip 32 may increase the pressure of the air 102 proximate the tip 32. The pressure differential between the relatively high pressure interior 40 proximate the tip 32 and the pressure exterior to the rotor blade 16 may thus be utilized to flow the air 102 through the purge conduits 100, as discussed below.

Thus, to reduce noise at the tip 32 of the rotor blade 16, such as noise caused by tip flow vortices 50, at least a portion of the air 102 in the interior 40 may be flowed through the purge conduits 100 and exhausted from the purge conduits 100. The exhausted air 102 may reduce the noise at the tip 32 of the rotor blade 16 by, for example, interfering with the tip flow vortices 50, as discussed above, or otherwise generally acting to reduce noise.

As shown in FIGS. 5 and 6, a purge conduit 100 according to the present disclosure may comprise an inlet 112 and an outlet 114. The inlet 112 may be generally adjacent to the interior 40 and defined in the interior surface 38 of the tip 32, while the outlet 114 may be generally spaced from the interior 40 and defined in the exterior surface 36 of the tip 32. Thus, the inlet 112 and the outlet 114 may generally define the purge conduit 100 therebetween, such that the purge conduit 100 extends between the inlet 112 and the outlet 114. At least a portion of the air 102 flowing through the interior 40, such as at least a portion of the air 102 flowing towards the tip 32 due to centrifugal forces as discussed above, may enter the purge conduit 100 through the inlet 112 and flow through the purge conduit 100. This air 102 in the purge conduit 100, or at least a portion thereof, may then be exhausted from the purge conduit 100 through the outlet 114, and may thus reduce noise at the tip 32 as discussed above.

The purge conduit 100 according to the present disclosure may be defined in the tip 32 at any location on the tip 32. For example, in some embodiments as shown in FIGS. 2 through 7, a purge conduit 100 or a plurality of purge conduits 100 may be defined in the tip 32 generally adjacent to the pressure side 22 and/or generally adjacent to the suction side 24. The purge conduit 100 or purge conduits 100 may further generally follow the contour of the pressure side 22 and/or the suction side 24, if desired.

The purge conduit 100 according to the present disclosure may have any suitable shape and size. For example, in some embodiments as shown in FIGS. 2, 3, and 5 through 7, a purge conduit 100 may be a slot 122. The slot 122 may extend through any portion of the tip 32. For example, a slot 122 may extend through a portion of the tip 32 generally adjacent to the pressure side 22 and/or generally adjacent to the suction side 24, and/or may follow the contour of the pressure side 22 and/or the suction side 24, as shown and discussed above.

In other embodiments, as shown in FIG. 4, a purge conduit 100 may be a hole 124. The hole 124, or a plurality of holes 124, may be defined at any suitable location or locations on the tip 32. In some embodiments, a plurality of holes 124 may extend through a portion of the tip 32, similar to a slot 122 and as shown in FIG. 4. For example, a plurality of holes 124 may extend through a portion of the tip 32 generally adjacent to the pressure side 22 and/or generally adjacent to the suction side 24, and/or may follow the contour of the pressure side 22 and/or the suction side 24, as shown and discussed above with regard to the slot 122.

As mentioned above, it should be understood that the slots 122 and holes 124 according to the present disclosure may have any suitable shapes and sizes. For example, the slots 122 and holes 124 may have cross-sectional shapes that are generally rectangular or square, oval or circular, triangular, or any other suitable polygonal shape.

In some embodiments, the purge conduit 100 according to the present disclosure may taper between the inlet 112 and the outlet 114. For example, in exemplary embodiments, the taper may be such that the inlet 112 is generally larger than the outlet 114, such that air 102 flowing through the purge conduit 100 is accelerated, as shown in FIGS. 5 and 6. In other embodiments, however, the taper may be such that the inlet 112 is generally smaller than the outlet 114. The taper of the purge conduit 100 may be through the entire length of the purge conduit 100, or through a portion thereof.

It should be understood, however, that the purge conduit 100 according to the present disclosure need not taper, and may, for example, have a generally constant area between the inlet 112 and the outlet 114 or have any other suitable configuration.

As shown in FIG. 5, in some embodiments, a purge conduit 100 according to the present disclosure may extend between the inlet 112 and the outlet 114 generally perpendicularly to the tip 32, such as generally perpendicular to the exterior surface 36 of the tip 32. Thus, air 102 exhausted from the purge conduit 100 may be exhausted generally perpendicularly to the tip 32. In other embodiments, however, as shown in FIG. 6, a purge conduit 100 according to the present disclosure may extend between the inlet 112 and the outlet 114 at an angle 130 from perpendicular to the tip 32. As shown, in some embodiments, the angle 130 may be in the range between approximately 0° and approximately 80°, or between approximately 0° and approximately 60°. The angle 130 may be such that air 102 exhausted from the purge conduit 100 is exhausted generally towards, for example, the pressure side 22, suction side 24, leading edge 26, or trailing edge 28, or may be such that air 102 exhausted from the purge conduit 100 is exhausted generally away from, for example, the pressure side 22, suction side 24, leading edge 26, or trailing edge 28.

It should be understood that the purge conduit 100 of the present disclosure is not limited to the above disclosed range of angles 130, and rather that any suitable angle 130 or range of angles 130 is within the scope and spirit of the present disclosure.

As discussed above, a purge conduit 100 according to the present disclosure may be defined in the tip 32 at any location on the tip 32. In some exemplary embodiments, a purge conduit 100 may defined at a particular chord-wise location in the tip 32. For example, as discussed above, the tip 32 may define a local chord 46. In some exemplary embodiments, a purge conduit 100 or purge conduits 100 may be located between approximately 0% and approximately 80%, between approximately 5% and approximately 80%, between approximately 0% and approximately 60%, or between approximately 5% and approximately 60% of the local chord 46 from the trailing edge 28.

The present disclosure is further directed to a method for reducing rotor blade 16 noise. For example, the method may reduce noise at the tip 32, such as noise caused by tip flow vortices 50, as discussed above. The method may include, for example, the step of flowing air 102 through the interior 40 of the rotor blade 16, as discussed above. Further, the method may include, for example, the step of flowing at least a portion of the air 102 through at least one purge conduit 100, or a plurality of purge conduits 100, defined proximate the tip 32 of the rotor blade 16. For example, the purge conduits 100 may be defined in the tip 32 of the rotor blade 16, as discussed above. Alternatively, the purge conduits 100 may be defined in another surface of the rotor blade 16, such as the pressure side 24, suction side 26, leading edge 26, or trailing edge 28 proximate the tip 32, such as between approximately 0% and approximately 5% of the span 44 from the tip 32. Further, the method may include, for example, the step of exhausting at least a portion of the air 102 from the purge conduit 100 or purge conduits 100. The air 102 exhausted from the purge conduits 100 may reduce noise at the tip 32 by, for example, interfering with a tip flow vortex 50 or a plurality of tip flow vortices 50, as discussed above.

In some embodiments, the method may include, for example, the step of flowing air 102 into the interior 40. For example, air 102 may be flowed into the interior 40 through at least one intake conduit 106 or a plurality of intake conduits 106, as discussed above. The intake conduits 106 may be defined in a stagnation zone 104, as discussed above.

The present rotor blade 16 and method for reducing rotor blade 16 noise may have a relatively significant impact on the noise at the tip 32 of the rotor blade 16. For example, in some embodiments, the inclusion of purge conduits 100 as described herein has been shown to reduce the average turbulent kinetic energy at the tip 32. For example, the average turbulent kinetic energy at the tip 32 may be significantly reduced. This reduction causes a decrease in noise at the tip 32. Additionally, the inclusion of purge conduits 100 as described herein has been shown to increase the power of the rotor blade 16 at the tip 32.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. 

1. A rotor blade for a wind turbine, comprising: a body having exterior surfaces defining a pressure side, a suction side, a leading edge, and a trailing edge extending between a tip and a root, the surfaces further defining an interior; and, at least one purge conduit defined in the tip and configured for exhausting air from the interior such that the air generally reduces noise at the tip.
 2. The rotor blade of claim 1, wherein the purge conduit tapers between an inlet and an outlet.
 3. The rotor blade of claim 1, wherein the purge conduit extends at an angle from perpendicular to the tip in the range between approximately 0° and approximately 80°.
 4. The rotor blade of claim 1, wherein the purge conduit is generally adjacent to the pressure side.
 5. The rotor blade of claim 1, wherein the purge conduit is generally adjacent to the suction side.
 6. The rotor blade of claim 1, further comprising a plurality of purge conduits.
 7. The rotor blade of claim 1, wherein the purge conduit is a slot.
 8. The rotor blade of claim 1, wherein the purge conduit is a hole.
 9. The rotor blade of claim 1, wherein the tip defines a local chord, and wherein the purge conduit is located between approximately 0% and approximately 80% of the local chord from the trailing edge.
 10. The rotor blade of claim 1, further comprising a stagnation zone defined on an exterior surface of the body, the stagnation zone defining at least one intake conduit configured to flow air to the interior of the body.
 11. The rotor blade of claim 10, wherein the body defines a span, and wherein the at least one intake conduit is located between approximately 0% and approximately 5% of the span from the tip.
 12. A wind turbine, comprising: at least one rotor blade, the at least one rotor blade comprising: a body having exterior surfaces defining a pressure side, a suction side, a leading edge, and a trailing edge extending between a tip and a root, the surfaces further defining an interior; and, at least one purge conduit defined in the tip and configured for exhausting air from the interior such that the air generally reduces noise at the tip.
 13. The wind turbine of claim 12, wherein the purge conduit tapers between an inlet and an outlet.
 14. The wind turbine of claim 12, wherein the purge conduit extends at an angle from perpendicular to the tip in the range between approximately 0° and approximately 80°.
 15. The wind turbine of claim 12, further comprising a plurality of purge conduits.
 16. The wind turbine of claim 12, wherein the tip defines a local chord, and wherein the purge conduit is located between approximately 0% and approximately 80% of the local chord from the trailing edge.
 17. The wind turbine of claim 12, further comprising a stagnation zone defined on an exterior surface of the body, the stagnation zone defining at least one intake conduit configured to flow air to the interior of the body.
 18. The wind turbine of claim 17, wherein the body defines a span, and wherein the at least one intake conduit is located between approximately 0% and approximately 5% of the span from the tip.
 19. A method for reducing rotor blade noise, the method comprising: flowing air through an interior of the rotor blade, the rotor blade comprising a body having exterior surfaces defining a pressure side, a suction side, a leading edge, and a trailing edge extending between a tip and a root, the surfaces further defining the interior; flowing at least a portion of the air through at least one purge conduit defined proximate the tip of the rotor blade; and exhausting at least a portion of the air from the purge conduit such that the air interferes with a tip flow vortex and generally reduces noise at the tip.
 20. The method of claim 19, further comprising flowing air into the interior through at least one intake conduit, the intake conduit defined in a stagnation zone, the stagnation zone defined on an exterior surface of the body. 